Description:
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The List of pool directives for PHP-FPM configuration at https://www.php.net/manual/en/install.fpm.configuration.php documents several process management directives. While the pm=static case seems fairly simple, the whole thing looks quite complicated. Unfortunately, neither the PHP manual nor the file comments are particularly clear, in particular for the following directives:


pm string
Choose how the process manager will control the number of child processes. Possible values: static, ondemand, dynamic. This option is mandatory.

static - the number of child processes is fixed (pm.max_children).

ondemand - the processes spawn on demand (when requested, as opposed to dynamic, where pm.start_servers are started when the service is started.

dynamic - the number of child processes is set dynamically based on the following directives: pm.max_children, pm.start_servers, pm.min_spare_servers, pm.max_spare_servers.

pm.max_children int
The number of child processes to be created when pm is set to static and the maximum number of child processes to be created when pm is set to dynamic. This option is mandatory.

This option sets the limit on the number of simultaneous requests that will be served. Equivalent to the ApacheMaxClients directive with mpm_prefork and to the PHP_FCGI_CHILDREN environment variable in the original PHP FastCGI.

pm.start_servers int
The number of child processes created on startup. Used only when pm is set to dynamic. Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2.

pm.min_spare_servers int
The desired minimum number of idle server processes. Used only when pm is set to dynamic. Also mandatory in this case.

pm.max_spare_servers int
The desired maximum number of idle server processes. Used only when pm is set to dynamic. Also mandatory in this case.



At least 2 things could greatly clarify:
1. Defining the effect of pm.min_spare_servers
2. Explaining the difference between child processes and server processes

Test script:
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This does not report a behavioral bug.